1. Field of the Invention
This invention relates to a novel light modulation device, which exhibits absorption characteristics for absorbing light having a specific wavelength and is capable of modulating light by the effect of the absorption characteristics.
2. Description of the Related Art
As light modulation devices, which exhibit absorption characteristics for absorbing light having a specific wavelength and are capable of modulating light by the effect of the absorption characteristics, for example, interference filters, such as etalons, have been used in practice. However, conventional interference filters are required to have a high level of smoothness and a high level of a film thickness accuracy. Therefore, the conventional interference filters are not always easy to produce, and costs of the conventional interference filters are not capable of being kept low. Also, the conventional interference filters are not always capable of being formed as filters having a large area. Further, since structures of the conventional interference filters are fixed, the light modulation characteristics of the conventional interference filters are fixed. Therefore, in cases where the wavelength of the light, which is to be absorbed (or transmitted) varies, a different interference filter must be prepared. The conventional interference filters are thus not capable of flexibly coping with alterations in design of optical systems, and the like.
In view of the above circumstances, a light modulation device for performing the light modulation in a state, in which a fluid is filled in a fine hole body having fine holes (nodes) of diameters falling within the range of 1.0 μm to 1.6 μm, has been proposed in, for example, International Patent Publication No. WO2002/082042. The proposed light modulation device has the fine holes having the diameters larger than light wavelengths, exhibits a photonic crystal structure, and modulates the light by the interference effect of the photonic crystal.
Also, a light modulation device for performing the light modulation in a state, in which a fluid is filled in a vessel provided with a pair of light transmissive wall bodies located at a spacing from each other with respect to an optical path direction such that the distance of the spacing is capable of being altered, has been proposed in, for example, Japanese Unexamined Patent Publication No. 2001-174719. With the proposed light modulation device, multiple reflection (resonance) occurs the pair of the light transmissive wall bodies, multiple interference occurs, the light having a specific wavelength is absorbed, and the light is thereby modulated.
With each of the light modulation devices described in, for example, International Patent Publication No. WO2002/082042 and Japanese Unexamined Patent Publication No. 2001-174719, the light modulation characteristics are capable of being altered through alteration of the kind of the fluid filled in the fine hole body or the vessel. However, with each of the light modulation devices described in, for example, International Patent Publication No. WO2002/082042 and Japanese Unexamined Patent Publication No. 2001-174719, it is not always possible to perform high-definition, high-separation light modulation capable of being achieved by the etalons, and the light modulation characteristics appropriate for optical filters are not always capable of being obtained.